Machine control system for milling arched roof structures

ABSTRACT

A control system may be provided for a machine having a swivel chair, a positioning member attached to the swivel chair, a wrist attached to the positioning member, and a cutting head. The control system may include at least one actuator capable of extending and swinging the swivel chair. The control system may also include a lift actuator capable of pivoting the positioning member, a gear mechanism capable of rotating the wrist, and a controller in communication with the swivel chair actuator, the lift actuator, and the wrist actuator. The controller may be capable of determining an excavation pass having a trajectory made from sequential vector paths, and directing the swivel chair actuator, the lift actuator, and the wrist actuator to selectively move the cutting head such that a rotation axis of the cutting head follows the trajectory through each vector path of the excavation pass to form a structure.

TECHNICAL FIELD

The present disclosure relates generally to a machine, and more particularly, to a system for controlling a machine to create structure having an arcuate surface.

BACKGROUND

One manner of forming tunnels in a hard-rock mining operation is to repetitively pass a cutting head of a mining machine across a vertical rock face in front of the mining machine as the mining machine advances toward the rock face. For example, the cutting head may be passed across the rock face in a “figure-8” pattern having a lower section and an upper section. This may consist of moving the cutting head from a centralized neutral position to a middle left edge of a tunnel, then down to a left floor edge, then to a right floor edge, then back up to a middle right edge, and back to the centralized neutral position thereby completing the lower section; then moving from the centralized neutral position again to the middle left edge, then up to a left ceiling edge, then to the right ceiling edge, and then back down to the middle right edge. Moving the cutting head in this manner results in a rectangular-shaped tunnel having a flat floor, flat left-side wall, flat right-side wall, and a flat ceiling.

The resulting flat-ceiling tunnel, from the process described above, may be less than optimal. In particular, the flat-ceiling tunnel may be weak and require post-excavation shoring to hold up the ceiling because the upper corner spaces of the tunnel that are excavated at intersections of the flat ceiling and the flat left-side wall and flat right-side wall are not utilized. Additionally, the time and resources spent excavating these spaces is wasted.

An alternative method for creating tunnels is disclosed in Chinese Pat. No. CN103867205 (“the '205 patent publication”). In particular, the '205 patent publication discloses a mining machine that relies on a virtual reality system to remotely control cutting of an arched-ceiling in a mining tunnel. The virtual reality system uses a database and a remote console to plan a path of a cutting tool. The database includes “field” conditions and is used to generate samples that correspond to virtual instructions for the mining machine. The cutting tool path is then remotely implemented to produce the arched-ceiling tunnel.

Although the virtual reality system disclosed in the '205 patent publication may be beneficial for creating an arched-ceiling tunnel, the system may be inherently cumbersome and have corresponding data integrity issues. For example, the system may require the generation of a three dimensional model, with lighting, textures, and video images as inputs. These inputs are then compiled by modeling software and moved into a programming model, and must be further optimized by channel engines and additional simulation optimization. The '205 patent publication may also offer opportunities for modeling errors, which may cause cutting misalignment that can lead to incorrect material removal and/or machine damage.

The disclosed control system may be directed at overcoming one or more of the problems set forth above and/or other problems in the prior art.

SUMMARY

One aspect of the present disclosure is directed to a control system for a machine having a swivel chair, a positioning member attached to the swivel chair, a wrist attached to the positioning member, and a cutting head attached to the wrist. The control system may include at least one swivel chair actuator capable of extending the swivel chair along an extension axis and swinging the swivel chair about a swing axis that is substantially perpendicular to the extension axis. The control system may also include a lift actuator capable of pivoting the positioning member about a pivot axis, a gear mechanism capable of rotating the wrist about a wrist axis, and a controller in communication with the swivel chair actuator, the lift actuator, and the wrist actuator. The controller may be capable of determining an excavation pass having a trajectory made from sequential vector paths. The controller may also be capable of directing the swivel chair actuator, the lift actuator, and the wrist actuator to selectively move the cutting head such that a rotation axis of the cutting head follows the trajectory through each vector path of the excavation pass to form a structure.

Another aspect of the present disclosure is directed to a method for operating a machine having a cutting head. The method may include determining an excavation pass having a trajectory made from sequential vector paths. The method may also include directing a swivel chair actuator, a lift actuator, and a wrist actuator to selectively move the cutting head such that a rotation axis of the cutting head follows the trajectory through each vector path of the excavation pass to form a structure.

Another aspect of the present disclosure is directed to a machine. The machine may include a frame, a swivel chair pivotally connected to the frame, a positioning member attached to the swivel chair, and a wrist attached to the positioning member. The machine may also include an extension actuator capable of extending the swivel chair along an extension axis, and a swing actuator capable of swinging the swivel chair about a swing axis that is substantially perpendicular to the extension axis. The machine may additionally include a lift actuator capable of pivoting the positioning member about a pivot axis, and a gear mechanism capable of rotating the wrist about a wrist axis. The machine may further include a controller in communication with the extension actuator, the swing actuator, the lift actuator, and the wrist actuator. The controller may be capable of determining a first excavation pass having a first trajectory made from sequential vector paths that form an arcuate upper portion of a cross-section of a structure, and determining a second excavation pass having a second trajectory made from vector paths that form a lower portion of the cross-section of the structure. The controller may additionally be capable of directing the extension actuator, the swing actuator, the lift actuator, and the wrist actuator to selectively move the cutting head such that a rotation axis of the cutting head follows the first and second trajectories through each vector path of the first and second excavation passes to form the structure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an exemplary mining machine;

FIG. 2 is a top plan view of the mining machine of FIG. 1;

FIG. 3 is a schematic illustration of an exemplary control system that may be used with the mining machine of FIGS. 1 and 2;

FIG. 4 is a spatial representation of an exemplary milling operation that can be executed by the control system of FIG. 3; and

FIG. 5 is a process diagram of a portion of the exemplary milling operation of FIG. 4.

DETAILED DESCRIPTION

Referring to FIGS. 1 and 2, an exemplary machine 10 such as, for example, a machine for creating tunnels, roadways, or shafts in material (such as rock, for example), is depicted. In this regard, machine 10 may be any machine associated with various industrial applications, including, but not limited to, mining, agriculture, forestry, construction, and/or other industrial applications. Machine 10 may include a cutting head 11 that is configured to mill material by rotating a plurality of rotary cutters 12 about a common cutter axis 13. Cutting head 11 may be operatively connected to a cutter boom 15 that may be operatively connected to a frame 14. Frame 14 may be supported by one or more ground engaging drive mechanisms, such as tracks 16. One or more power sources (e.g., electric motors and/or engines—not shown) may be supported by frame 14 and used to produce mechanical and electrical power outputs for driving and controlling the other components of machine 10.

Rotary cutters 12 may be mounted on cutting head 11 to rotate about their own cutter axes 17, at the same time that cutting head 11 rotates about cutter axis 13. Cutter axes 17 may be substantially perpendicular to cutter axis 13 in some embodiments, and declined away from an exposed axial end face 18 of cutting head 11 in other embodiments. Cutting head 11 and rotary cutters 12 may be moved to engage a cutting surface in front of machine 10 at any orientation. However, in order to promote efficient and damage-free operation, cutting head 11 should be controlled to move within a cutting plane that is aligned with cutter axis 13. That is, cutting head 11 may engage material in a direction generally perpendicular to axial end face 18. In at least one embodiment, a preferred cutting orientation may be defined as an orientation in which cutter axis 13 is substantially parallel to the material face being cut, and cutter axes 17 of rotary cutters 12 are substantially perpendicular to the face.

Cutting head 11 may be connected to cutter boom 15 by way of a wrist 19, a positioning member 22, and a swivel chair 24. Wrist 19 may be directly connected to cutting head 11 and configured to rotate cutting head 11 about a wrist axis 20 in order to maintain cutting head 11 in the preferred cutting orientation described above. Positioning member 22 may be configured to move wrist 19 and cutting head 11 up and down via pivoting about a pivot axis 23. Swivel chair 24 may be configured to swing cutting head 11, wrist 19, and positioning member 22 left and right about a swing axis 25. In some embodiments, swivel chair 24 may also extend and retract cutting head 11, wrist 19, and positioning member 22 along an extension axis 26. Swivel chair 24 may be moved with the assistance of one or more extension actuators 30 and swing actuators 31. Positioning member 22 may be moved with the assistance of one or more lift actuators 32. Rotation of wrist 19 may be achieved by way of a gear mechanism 33, which can be driven by one or more motors (e.g., hydraulic or electric motors—not shown).

As shown in FIG. 3, a controller 34 may be in communication with extension actuators 30, swing actuators 31, lift actuators 32, and gear mechanism 33 via a control system 35. Controller 34 may be capable of causing actuators 30-32 and gear mechanism 33 to move (e.g., via electric and/or hydraulic circuitry), thereby creating desired movements of cutting head 11. Controller 34 may be capable of causing movements of actuators 30-32 and gear mechanism 33 via electrical command signals directed to the actuators and/or to hydraulic valves (e.g., a swing valve 36, an extend valve 38, a lift valve 40, a wrist rotate valve 42, etc.) associated with the actuators. In this way, controller 34 may regulate the rotating, swinging, lifting, pivoting, extending, and retracting movements of machine 10 during a milling operation.

Controller 34 may be an electronic controller that operates in a logical fashion to perform operations, execute control algorithms, store and retrieve data and other desired operations. Controller 34 may include or access memory, secondary storage devices, processors, and any other components for running an application. Various other circuits may be associated with controller 34 such as power supply circuitry, signal conditioning circuitry, driver circuitry, and other types of sensory circuitry.

The term “controller” is meant to be used in its broadest sense to include one or more controllers and/or microprocessors that are associated with the machine 10 and that may cooperate in controlling various functions and operations of machine 10. Controller 34 may utilize one or more data maps relating to the kinematics of machine 10 and the environment in which machine 10 may operate.

Controller 34 may have a milling database stored in memory that includes one or more pre-set milling operations organized by cross-sectional size, shape, and/or type. Each operation may consist of excavation passes having any number of sequential milling vector paths. For example, the milling database may include a tunnel milling operation corresponding to a tunnel having a lower rectangular shape and an upper arcuate shape. Each operation stored in the milling database may have a corresponding cut-vector table, which represents linear trajectories of cutting head 11 required to create each of the sequential vector paths that make up the operation. To move cutting head 11 along a particular linear vector path, controller 34 may reference the database to determine a corresponding infeed depth, a corresponding horizontal swing (e.g., left swing, right swing) and a corresponding vertical movement (e.g., raise, lower, pivot). Controller 34 may process the respective vectors of the cut-vector table into corresponding command signals based on a detected position of machine 10, known kinematics of machine 10, and detected environmental data.

Machine 10 may be equipped with one or more sensors that provide data indicative of various operating parameters of machine 10 and/or aspects of the environment in which machine 10 may be operating in. The term “sensor” is meant to be used in its broadest sense to include one or more sensors and related components associated with machine 10 that cooperate to sense various functions, operations, and operating characteristics.

In the example shown in FIG. 3, a position sensor 43 is included in control system 35. Position sensor 43 may be used to detect a position and/or orientation (e.g., a heading, pitch, roll or tilt, and yaw) of machine 10, and more particularly of cutting head 11. For example, position sensor 43 may be a GPS sensor that provides an absolute location and/or orientation of cutting head 11 in a three-dimensional coordinate system. In the same or another example, position sensor 43 may include one or more sensing elements that detect motion of the components of machine 10, which can then be used to determine the location and/or orientation of cutting head 11. For example, position sensor 43 could include one or more sensing elements associated with cutting head 11, wrist 19, drum 22, and/or swivel chair 24 (e.g., associated with the actuators and/or mechanisms that move these components). These sensing elements may be used to detect swinging, rotating, lifting, and/or extending movements. In the same or other embodiments, sensing elements may detect fluid pressures, valve positions, accelerations, etc. associated with actuators 30-32 and gear mechanism 33.

The signals from position sensor 43 may be used to determine a pose (e.g., a heading, pitch, roll or tilt, and/or yaw) of cutting head 11 relative to features of the environment (e.g., the rock face to be cut by cutting head 11) around machine 10. For example, controller 34 may compare the three-dimensional location and/or orientation of machine 10 to locations, sizes, shapes, and/or orientations of known features in the environment using a database of maps stored in the memory of controller 34.

The database stored in the memory of controller 34 may be updated during operation of machine 10, such that the maps reflect changes made to the environment by machine 10. Controller 34 may rely on signals from position sensor 43 for this purpose. In some embodiments, controller 34 may also rely on one or more environmental sensors 44 for this purpose.

Environment sensor 44 may include one or more sensing elements that interact with the working environment of machine 10. For example, machine 10 may utilize lasers and prisms with the assistance of field engineering and surveying equipment. Based upon a known position of the lasers and reflected light from the prisms, a pose of cutting head 11 relative to the known features may be determined. In other embodiments, environment sensor 44 may be a RADAR sensor, a SONAR sensor, a LIDAR sensor, and/or a camera vision sensor. Environment sensor 44 may generate data that is received by controller 34 and used to determine the position and orientation of cutting head 11 relative to specific cutting faces shown in FIGS. 1 and 2. Such faces may include a floor face 50, an upper cutting face 51, a lower cutting face 52, and a ceiling face 54.

FIG. 4 spatially represents a target trajectory and orientation of cutting head 11 relative to faces 50-54 during an exemplary milling operation that produces an arched-roof tunnel. FIG. 5 illustrates a process of a portion of the exemplary milling operation of FIG. 4. Additional description of FIGS. 4 and 5 will be provided in detail in the following section to further illustrate the concepts of this disclosure.

INDUSTRIAL APPLICABILITY

The disclosed control system may be beneficial to mining machines that are used to create structures, such as tunnels, in hard-rock applications. Control system 35 may improve the efficiency of the mining machines by automatically planning and controlling trajectories of a cutting head. In the disclosed embodiment, cutting head 11 may be controlled to create an arched-ceiling structure and/or tunnel. Operation of control system 35 will now be explained with reference to FIGS. 3 and 4.

An exemplary trajectory 400 is shown in FIG. 4, which can be used to control operation and movement of cutting head 11 during a milling operation. As can be seen from FIG. 4, trajectory 400 includes a lower excavation pass 402 used to create a generally rectangular space in lower cutting face 52, and an upper excavation pass 404 used to create an arcuate space in upper cutting face 51 that lies on top of the rectangular space in lower cutting face 52 and forms an arched-ceiling. Although excavation pass 402 may generally be completed first, it is contemplated that lower excavation pass 404 could precede upper excavation pass 402, if desired. Similarly, it is contemplated that trajectory 400 may be completed in a direction opposite to that as shown by FIG. 4, if desired.

Each of excavation passes 402 and 404 may include a plurality of vector paths that are arranged in sequence to form a completed target trajectory for cutting head 11. For example, excavation pass 402 may include vector paths 101-108, while excavation pass 404 may include vector paths 109-118. Each vector path may be separated by a target position that serves as a starting position of one vector path and an ending position of another vector path. Stated another way, the trajectory of cutting head 11 follows each vector path between respective target positions. Each of the target positions, as well as the trajectory between the positions, may be stored in a cut-vector table described earlier. Furthermore, the necessary machine command signals to move along vector paths and between the target positions may also be stored in the cut-vector table described earlier. In this way, a spacing between and locations of the target positions may be set by controller 34 to mill any desired shape with any desired resolution. That is, to adjust the resolution controller 34 may increase the amount of target positions thereby decreasing the spacing between them and increasing the resolution of the resultant shape.

In other embodiments, target positions may be established one at a time, without storing target positions in the cut-vector table described earlier. This may be particularly advantageous to prevent misalignment of cutting head 11 as a result of data distortion and/or integrity issues. For example, controller 34 may determine a first target position along the target trajectory and commence the milling operation before determining the remaining interstitial target positions. That is, controller 34 may then determine the next target positions based of the actual position and pose of cutting head 11, as may be determined with the assistance of sensors 43, 44. For example, controller 34 may determine the next target position as a look-ahead target position and move cutting head 11 towards the next target position along the vector path between the actual position of cutting head 11 and the next target position. In other embodiments, Controller 34 may repeatedly determine new target positions along the trajectory according to a pre-established time interval rather than a particular distance traveled and/or proximity to the next target position. For example, every 20 milliseconds controller 34 may determine the next target position along the target trajectory and simultaneously generate the next vector path between the actual position of cutting head 11 and the next target point. In this way, by repeatedly establishing next target positions along the target trajectory and next vector paths to move cutting head 11 controller 34 may compensate for milling misalignment, uneven force transfer, unexpected positioning, and/or positioning errors by accounting for the actual position and adjusting the pose of cutting head 11. It is contemplated, that the specific time interval cycle may be adjusted to control milling of shapes with any desired resolution (i.e., smoothness).

Controller 34 may determine the target positions of corresponding vector paths according to a desired cross sectional size, shape, and cutting radius of cutting head 11. For example, the perimeter of the desired structural shape may be digitized based on a desired resolution, and the complete trajectory may be established by insetting the perimeter towards the center by a distance equal to the radius of cutting head 11. The cycle of target positions may fall on the inset perimeter such that the final milled shape is substantially similar to the shape defined by the original perimeter. This process may be repeated iteratively, as a cycle performed over discrete time intervals, until cutting head 11 has moved along the entirety of the inset perimeter.

Target positions of an arcuate structure, such as an arched ceiling of a tunnel, may be determined by controller 34 according to a similar process. In particular, controller 34 may determine the perimeter of an arcuate shape by establishing an initial target position, an ending target position, and a radius point. The radius point may not be a target position, rather it is used to assist controller 34 with determining the curvature of the arcuate path between the initial target position and the ending target position. The initial target position may correspond to a target position along the inset perimeter used to establish the height of a sidewall of a tunnel. Similarly, the ending target position may correspond to a target position along the inset perimeter used to establish the height of the opposite sidewall of the tunnel. Stated another way, the initial target position and ending target position are located along the inset perimeter at an intersection between an arcuate path used to define an arched ceiling and a vertical linear path used to define a sidewall surface of a tunnel. To determine the radius point controller 34 may extrapolate two upper vector paths between the desired maximum tunnel height point and the two desired vertical sidewall heights, respectively. Controller 34 may then determine the midpoint of each upper vector path and extrapolate two additional central vector paths that are substantially perpendicular to the upper vector paths, respectively. The interior intersection of the central vector paths may be the radius point used to define the curvature of the arcuate path.

The arcuate path may correspond to an arc of a perfect circle that extends from the top left (i.e., from the initial target position of vector path 109) and terminates at the top right (i.e., the ending target position of vector path 118). With an established initial target position, ending target position, and radius point, controller 34 may generate arcuate paths corresponding to any type of curved shape. For example, an arc of an imperfect circle, such as an oval, a parabola, or an ellipse may be used as the basis of the arcuate path.

Controller 34 may be configured to adjust the pose of cutting head 11 based on the trajectory of each vector path in each excavation pass. In particular, controller 34 may adjust swinging, lifting, lowering, pivoting, and/or rotating of cutting head 11, such that cutter axis 13 of cutting head 11 follows and is aligned with the trajectory of each vector path.

For example, at a start of excavation pass 402, controller 34 may initiate an outward extension of swivel chair 24 to position cutting head 11 at the desired cutting depth at a start position of vector path 101, while simultaneously initiating a leftward swinging of swivel chair 24 to move cutter axis 13 of cutting head 11 along the trajectory of vector path 101 towards vector path 102. When cutting head 11 nears the end position of vector path 101 and the start position of vector path 102 controller 34 may need to reorient cutting head 11 in preparation for completing vector path 102. In particular, controller 34 may need to cause wrist 19 to rotate counter-clockwise (relative to the perspective of FIG. 1) by about 90°, such that cutter axis 13 maintains its alignment with the trajectory of vector path 102. When cutting head 11 moves along vector path 102, controller 34 may initiate a downward pivot of positioning member 22 to move cutter axis 13 of cutting head 11 along the trajectory of vector path 102 towards vector path 103.

When cutting head 11 moves along vector path 103, controller 34 may initiate a downward pivot of positioning member 22 to move cutter axis 13 of cutting head 11 along the trajectory of vector path 103 and through vector path 104. When cutting head 11 nears the end position of vector path 104 controller 34 may need to reorient cutting head 11 in preparation for completing vector path 105 such that cutter axis 13 maintains its alignment with the trajectory of vector path 105 (e.g., 90° counter-clockwise rotation).

When cutting head 11 moves along vector path 105, controller 34 may initiate a rightward swinging of swivel chair 24 to move cutter axis 13 of cutting head 11 along the trajectory of vector path 105 towards vector path 106. When cutting head 11 nears the end position of vector path 105, controller 34 may need to reorient cutting head 11 in preparation for completing vector path 106 such that cutter axis 13 maintains its alignment with the trajectory of vector path 106 (e.g., 90° counter-clockwise rotation).

When cutting head 11 moves along vector path 106, controller 34 may initiate an upward pivot of positioning member 22 to move cutter axis 13 of cutting head 11 along the trajectory of vector path 106 towards vector path 107. When cutting head 11 moves along vector path 107, controller 34 may initiate an upward pivot of positioning member 22 to move cutter axis 13 of cutting head 11 along the trajectory of vector path 107 towards vector path 108. When cutting head 11 nears the end position of vector path 107 controller 34 may need to reorient cutting head 11 in preparation for completing vector path 108 such that cutter axis 13 maintains its alignment with the trajectory of vector path 108 (e.g., 90° counter-clockwise rotation).

When cutting head 11 moves along vector path 108, controller 34 may initiate a leftward swinging of swivel chair 24 to move cutter axis 13 of cutting head 11 along the trajectory of vector path 108, towards the start position of vector path 101. When cutting head 11 reaches the start position of vector path 101 the lower excavation pass 402 may be complete.

After completing lower excavation pass 402, controller 34 may initiate the start of upper excavation pass 404. Controller 34 may move cutting head 11 along previously milled vector path 101 towards vector path 109 as previously disclosed. When cutting head 11 nears the start position of vector path 109, controller 34 may need to reorient cutting head 11 in preparation for completing vector path 109. In particular, controller 34 may need to cause wrist 19 to rotate clockwise (relative to the perspective of FIG. 1) by about 90°, such that cutter axis 13 maintains its alignment with the trajectory of vector path 109.

When cutting head 11 moves along vector path 109, controller 34 may initiate an upward pivot of positioning member 22 to move cutter axis 13 of cutting head 11 along the trajectory of vector path 109 towards vector path 110. When cutting head 11 nears the end position of vector path 109 controller 34 may need to reorient cutting head 11 in preparation for completing vector path 110. In particular, controller 34 may need to cause wrist 19 to rotate clockwise (relative to the perspective of FIG. 1) by about 20°, such that cutter axis 13 maintains its alignment with the trajectory of vector path 110.

When cutting head 11 moves along vector path 110, controller 34 may initiate an upward pivot of positioning member 22 and a rightward swinging of swivel chair 24 to move cutter axis 13 of cutting head 11 along the trajectory of vector path 110 towards vector path 111. When cutting head 11 nears the end position of vector path 110, controller 34 may need to reorient cutting head 11 in preparation for completing vector path 111 such that cutter axis 13 maintains its alignment with the trajectory of vector path 111 (e.g., 20° clockwise rotation).

When cutting head 11 moves along vector path 111, controller 34 may initiate an upward pivot of positioning member 22 and a rightward swinging of swivel chair 24 to move cutter axis 13 of cutting head 11 along the trajectory of vector path 111 towards vector path 112. When cutting head 11 nears the end position of vector path 111, controller 34 may need to reorient cutting head 11 in preparation for completing vector path 112 such that cutter axis 13 maintains its alignment with the trajectory of vector path 112 (e.g., 20° clockwise rotation).

When cutting head 11 moves along vector path 112, controller 34 may initiate an upward pivot of positioning member 22 and a rightward swinging of swivel chair 24 to move cutter axis 13 of cutting head 11 along the trajectory of vector path 112 towards vector path 113. When cutting head 11 nears the end position of vector path 112, controller 34 may need to reorient cutting head 11 in preparation for completing vector path 113 such that cutter axis 13 maintains its alignment with the trajectory of vector path 113 (e.g., 20° clockwise rotation).

When cutting head 11 moves along vector path 113, controller 34 may initiate an upward pivot of positioning member 22 and a rightward swinging of swivel chair 24 to move cutter axis 13 of cutting head 11 along the trajectory of vector path 113 towards vector path 114. When cutting head 11 nears the end position of vector path 113, controller 34 may need to reorient cutting head 11 in preparation for completing vector path 114 such that cutter axis 13 maintains its alignment with the trajectory of vector path 114 (e.g., 20° clockwise rotation).

When cutting head 11 moves along vector path 114, controller 34 may initiate a downward pivot of positioning member 22 and a rightward swinging of swivel chair 24 to move cutter axis 13 of cutting head 11 along the trajectory of vector path 114 towards vector path 115. When cutting head 11 nears the end position of vector path 114, controller 34 may need to reorient cutting head 11 in preparation for completing vector path 115 such that cutter axis 13 maintains its alignment with the trajectory of vector path 115 (e.g., 20° clockwise rotation).

When cutting head 11 moves along vector path 115, controller 34 may initiate a downward pivot of positioning member 22 and a rightward swinging of swivel chair 24 to move cutter axis 13 of cutting head 11 along the trajectory of vector path 115 towards vector path 116. When cutting head 11 nears the end position of vector path 115, controller 34 may need to reorient cutting head 11 in preparation for completing vector path 116 such that cutter axis 13 maintains its alignment with the trajectory of vector path 116 (e.g., 20° clockwise rotation).

When cutting head 11 moves along vector path 116, controller 34 may initiate a downward pivot of positioning member 22 and a rightward swinging of swivel chair 24 to move cutter axis 13 of cutting head 11 along the trajectory of vector path 116 towards vector path 117. When cutting head 11 nears the end position of vector path 116, controller 34 may need to reorient cutting head 11 in preparation for completing vector path 117 such that cutter axis 13 maintains its alignment with the trajectory of vector path 117 (e.g., 20° clockwise rotation).

When cutting head 11 moves along vector path 117, controller 34 may initiate a downward pivot of positioning member 22 and a rightward swinging of swivel chair 24 to move cutter axis 13 of cutting head 11 along the trajectory of vector path 117 towards vector path 118. When cutting head 11 nears the end position of vector path 117, controller 34 may need to reorient cutting head 11 in preparation for completing vector path 118 such that cutter axis 13 maintains its alignment with the trajectory of vector path 118 (e.g., 20° clockwise rotation).

When cutting head 11 moves along vector path 118, controller 34 may initiate a downward pivot of positioning member 22 and a rightward swinging of swivel chair 24 to move cutter axis 13 of cutting head 11 along the trajectory of vector path 118. When cutting head 11 nears the end position of vector path 118, controller 34 may need to reorient cutting head 11 in preparation for a second lower excavation pass (not illustrated) and/or a second upper excavation pass (not illustrated). The second excavation passes may be similar to the lower excavation pass 402 and upper excavation pass 404, respectively. The second excavation passes may be inset towards the center of the tunnel by a pre-determined distance. Moreover, controller 34 may continue to move cutting head 11 along any number of successive and inset excavation passes (depending upon the desired cross sectional shape) until a milling operation is complete. For example, controller 34 may repetitively move cutting head 11 in a “figure-8” pattern consisting of lower excavation passes and upper excavation passes.

Lower excavation pass 402 and/or upper excavation pass 404 may be formed of any number of target positions that are dynamically updated while performing the particular excavation pass. FIG. 5 may disclose an exemplary process executed by controller 34 to perform upper excavation pass 404 by dynamically updating target positions while performing upper excavation pass 404. In particular, FIG. 5 may disclose a process to perform an arcuate milling cycle by repeatedly determining new target positions within a pre-determined time interval cycle. The arcuate milling cycle may start (Step 500) when controller 34 determines that cutting head 11 is positioned within a pre-determined proximity to an initial target position, such as target position 109 of FIG. 4. Controller 34 may activate an arc milling cycle (Step 502) and determine an arcuate path (Step 504) as previously disclosed. Controller 34 may then determine a first target position along the arcuate path that is proximate to the actual position of cutting head 11 (Step 506). Controller 34 may then set an appropriate pose of cutting head 11 (Step 508). Controller 34 may set an appropriate pose by determining a linear vector path from the actual position of cutting head 11 to the first target position and orienting cutting head 11 such that cutter axis 13 maintains its alignment along the vector path between the actual position of cutting head 11 and the first target position.

Controller 34 may then move cutting head 11 toward the first target position (Step 510). Controller 34 may move cutting head 11 toward the first target position by initiating downward and upward pivoting, rightward and leftward swinging, and clockwise and counterclockwise rotation of cutting head 11 as previously disclosed. Next, controller 34 may determine whether the arcuate path is completed (Step 512) based off an actual position of cutting head 11. When controller 34 determines that the arc trajectory is not completed (Step 512: No) controller 34 may determine a next target position by returning to Step 506. Controller 34 may repeatedly determine next target positions (Step 506), set an appropriate pose of cutting head 11 (Step 508), and move cutting head 11 toward the next target position (Step 510) continuously as a cycle until the entirety of the arcuate path is traveled. Controller 34 may execute steps 506, 508, 510, and 512 within a pre-determined time interval such that a next target position is continuously and dynamically established while performing the arc milling cycle. In this way, the resolution of a particular arcuate path may be modified by altering the time interval. For example, by decreasing the time interval a particular arcuate path may have a greater number of target positions and therefore a greater resolution. Additionally, controller 34 may account for misalignment of cutting head 11 by establishing the next vector path based off of an actual position of cutting head 11 and the next target position. When controller 34 determines that the arc trajectory is completed (Step 512: Yes) than controller 34 may end the arc milling cycle (Step 514).

Several benefits may be associated with the disclosed control system. Specifically, the disclosed control system may increase the efficiency of a mining operation by reducing the total quantity of material milled. Similarly, the disclosed control system may eliminate the need for post excavation shoring as a tunnel having an arched roof may be capable of structurally supporting itself without the need for costly and time consuming post excavation shoring. The linear vector paths may reduce the likelihood of data integrity issues, misalignment, miscalculated trajectories, etc. Similarly, by dynamically generating target positions according to time intervals and the actual position of cutting head 11 based off of actual positions the likelihood of data integrity issues, misalignment, miscalculated trajectories, etc. is reduced.

It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed control system. Other embodiments vvill be apparent to those skilled in the art from consideration of the specification and practice of the disclosed control system. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents. 

What is claimed is:
 1. A control system for a machine having a swivel chair, a positioning member coupled to the swivel chair, a wrist coupled to the positioning member, and a cutting head, the control system comprising: at least one swivel chair actuator configured to extend the swivel chair along an extension axis and to swing the swivel chair about a swing axis that is substantially perpendicular to the extension axis; a lift actuator configured to pivot the positioning member about a pivot axis; a gear mechanism configured to rotate the wrist about a wrist axis; and a controller in communication with the swivel chair actuator, the lift actuator, and the wrist actuator, the controller being configured to: determine an excavation pass having a trajectory made from a plurality of sequential vector paths; and direct the swivel chair actuator, the lift actuator, and the wrist actuator to selectively move the cutting head such that a rotation axis of the cutting head follows the trajectory through each vector path of the excavation pass to form a structure
 2. The control system of claim 1, wherein: the excavation pass is a first excavation pass that forms an arcuate upper portion of a cross-section of the structure; and the controller is further configured to: determine a second excavation pass having a trajectory made from a plurality of sequential vector paths; and direct the swivel chair actuator, the lift actuator, and the wrist actuator to selectively move the cutting head such that the rotation axis of the cutting head follows the trajectory of the second excavation pass through each vector path of the second excavation pass to form a lower portion of the cross-section of the structure.
 3. The control system of claim 2, wherein the controller is configured to move the cutting head to follow the trajectory of the second excavation pass and then the trajectory of the first excavation pass in a particular pattern.
 4. The control system of claim 1, wherein: the structure is a tunnel; each of the plurality of sequential vector paths includes a start target position and an end target position; wherein the start target position corresponds to an actual position of the cutting head; and the controller is configured to determine locations of the end target locations by determining a perimeter of a desired shape of the tunnel, offsetting the perimeter by a radius of the cutting head to extrapolate an inset perimeter, and continuously generating end target locations along the inset perimeter according to a time interval cycle.
 5. The control system of claim 4, further including an environment sensor configured to generate signals indicative of locations of features in an environment of the machine, wherein the controller is configured to determine the start and end target locations for each of the plurality of sequential vector paths based further on the signals.
 6. The control system of claim 5, wherein the controller is configured to determine the start and end target locations based further on a desired depth of the excavation pass.
 7. The control system of claim 4, wherein the perimeter is at least partially defined by an arc of a perfect circle.
 8. The control system of claim 1, wherein each of the plurality of vector paths are linear vector paths.
 9. The control system of claim 1, further including a position sensor configured to generate signals indicative of at least one of a position of the cutting head or an orientation of the cutting head, wherein the controller is configured to direct the swivel chair actuator, the lift actuator, and the wrist actuator to selectively move the cutting head based on the signals.
 10. A method for operating a machine having a cutting head, the method comprising: determining an excavation pass having a trajectory made from a plurality of sequential vector paths; and directing a swivel chair actuator of the machine, a lift actuator of the machine, and a wrist actuator of the machine to selectively move the cutting head such that a rotation axis of the cutting head follows the trajectory through each vector path of the excavation pass to form a structure.
 11. The method of claim 10, wherein: the excavation pass is a first excavation pass that forms an arcuate upper portion of a cross-section of the structure; and the method further includes determining a second excavation pass having a trajectory made from a plurality of sequential vector paths; and directing the swivel chair actuator, the lift actuator, and the wrist actuator to selectively move the cutting head such that the rotation axis of the cutting head follows the trajectory of the second excavation pass through each vector path of the second excavation pass to form a lower portion of the cross-section of the structure.
 12. The method of claim 11, wherein directing the swivel chair actuator, the lift actuator, and the wrist actuator to selectively move the cutting head includes directing the swivel chair actuator, the lift actuator, and the wrist actuator to selectively move the cutting head to follow the trajectory of the first excavation pass and then the trajectory of the second excavation pass in a particular pattern.
 13. The method of claim 10, wherein: the structure is a tunnel; each of the plurality of sequential vector paths includes a start target position and an end target position; wherein the start target position corresponds to an actual position of the cutting head; and determining the excavation pass includes determining locations of the end target locations by determining a perimeter of a desired shape of the tunnel, offsetting the perimeter by a radius of the cutting head to extrapolate an inset perimeter, and continuously generating end target locations along the inset perimeter according to a time interval cycle.
 14. The method of claim 13, further including sensing locations of features in an environment of the machine, wherein determining locations of the start target position and end target position includes determining locations of the start target position and end target position based on the locations of the features.
 15. The method of claim 14, wherein determining locations of the start target position and end target position includes determining locations of the start target position and end target position based further on a desired depth of the excavation pass.
 16. The method of claim 13, wherein the perimeter is at least partially defined by an arc of a circle.
 17. The method of claim 10, wherein each of the plurality of vector paths are linear vector paths.
 18. The method of claim 10, further including sensing at least one of a position and an orientation of the cutting head, wherein directing the swivel chair actuator, the lift actuator, and the wrist actuator to selectively move the cutting head includes directing the swivel chair actuator, the lift actuator, and the wrist actuator to selectively move the cutting head based on the at least one of the position and the orientation of the cutting head.
 19. A machine, comprising: a frame; a swivel chair pivotally connected to the frame; a positioning member coupled to the swivel chair; a wrist coupled to the positioning member; a cutting head coupled to the wrist; an extension actuator configured to extend the swivel chair along an extension axis; a swing actuator configured to swing the swivel chair about a swing axis that is substantially perpendicular to the extension axis; a lift actuator configured to pivot the positioning member about a pivot axis; a gear mechanism configured to rotate the wrist about a wrist axis; and a controller in communication with the extension actuator, the swing actuator, the lift actuator, and the wrist actuator, the controller being configured to: determine a first excavation pass having a first trajectory made from a plurality of sequential vector paths that forms an arcuate upper portion of a cross-section of a structure; determine a second excavation pass having a second trajectory made from a plurality of sequential vector paths that forms a lower portion of the cross-section of the structure; and direct the extension actuator, the swing actuator, the lift actuator, and the wrist actuator to selectively move the cutting head such that a rotation axis of the cutting head follows the first and second trajectories through each vector path of the first and second excavation passes to form the structure.
 20. The machine of claim 19, wherein: the structure is a tunnel; and the controller is configured to move the cutting head to follow the trajectory of the second excavation pass and then the trajectory of the first excavation pass in a particular pattern. 